1. Field of the Invention
This invention relates to the field of wiring systems for the distribution of electricity, particularly in office buildings, hospitals, and other types of public or commercial buildings. More specifically, it relates to simplified means for supporting wiring conduits in accordance with industry standards set forth in the National Electrical Code promulgated by the National Fire Protection Association in order to reduce the hazards associated with fires produced by faulty electrical distribution systems.
2. The Prior Art
Safety regulations require that wires carrying electrical current for operating lighting devices, motors, and other apparatus in buildings be strung safely and securely from each connection point to the next. The regulations require that connection points be within protective enclosures, such as outlet boxes, junction boxes, cabinets, and the like. In commercial buildings, in particular, the wires that extend from one enclosure to the next are routed within a hollow conduit for protection. Each end of each conduit is securely mechanically connected to one of the protective enclosures, unless the distance between two enclosures is so great that two or more conduits must be joined end-to-end to be long enough. Conduit couplings are required in runs longer than 10', consistent with the fact that conduit is typically made in 10' lengths. The wires within such long runs extend through the conduit fittings without interruption.
Conduits are typically rigid tubes having annular cross sections with prescribed cross-sectional dimensions and wall thicknesses, and they may be made of a suitable metallic or non-metallic material, provided such material meets requirements of structural and chemical integrity and is sufficiently resistant to moisture, fire, and corrosive chemical atmospheres.
Whatever the cross-sectional dimensions of a conduit, and whether it be metal or a non-metallic material, the Code states that the conduit must be securely fastened in place. This not only requires that each conduit be securely mechanically fastened to each enclosure at the point of entry, but it also requires that a long run of conduit that spans an open space be supported at least once every so many feet, depending on the type of conduit. For various types of metal conduit, there must be a support at least every 10 feet, with certain exceptions. For non-metallic conduit, the maximum permissible number of feet between supports varies according to the diameter of the conduit; conduit having a diameter in the range from 1/2" to 1" must be supported at least every 3', while conduit having a diameter of 6" need only be supported every 8'.
Of particular importance with respect to this invention is the requirement that each rigid conduit, whatever its diameter and whatever the material of which it is made, must be securely fastened within 3' of each enclosure or other conduit termination.
It is currently the practice, and has been for a long time, to fabricate support structures at a job site to meet all of the regulations for secure support structures. Moreover, the requirement to support conduit within 3' of each enclosure is often met by constructing, out of conveniently available material, a structure much shorter than 3'. Such ad hoc support structures are frequently quite complex, necessitating much cutting and assembly at the installation site, and, as a result, are costly, not only in terms of the amount of material used, but frequently even more so in terms of the amount of labor required to form the parts and to assemble them into a unitary structure and then connect them to the electrical components. Some ad hoc support structures are relatively simple to cut and assemble and may take only a short time to produce, but the number of such structures required in a typical commercial building is so great that the total time devoted to their construction and installation is very likely to be a substantial, though often unrecognized, expense.